tention, and automatically and instantaneously synthe sizes these analytic data into complex "presentations of sense." The three facts, changing aspects, movements of attention, and fixed phases, are involved in every state of finite consciousness; and, though it may at first seem first seem impossible, they are simultaneous. It at first seems that the changing aspects precede the movements of attention and cause them, also that the movement of attention consists in a series of starts and stops, and that each stop is followed by a fixed phase of the presentation. More careful observation, however, will show that the attention is in constant movement, moving more or less rapidly at times, and hence appearing at times more or less fixed, but never absolutely fixed. Moreover, the movements of attention may be considered the cause of the changing aspects just as logically as the effect of them. The eye moves voluntarily and involuntarily, and voluntary movement frequently seems to be composed of starts and stops; yet the eye cannot be held absolutely fixed, as anyone can verify by trial. The attention moves in harmony not with the action of the eye alone, but with the action of every sense-organ, both voluntarily and involuntarily. Like the movements of the eye, the voluntary movements of attention seem composed of starts and stops. When, however, any apparently single and separate movement of attention is carefully examined, it proves to be, like every other presentation, a continuum of still lower analytic data; and this fact holds true indefinitely. This shows not that a conscious state can be held under the focus of attention and subjected to an infinite process of division into infinitessimal elements approximating to zeros of consciousness; but that no fixed states of consciousness exist, and that the so-called analysis is a process of constant change in which the component elements are but moments. The vanishing and emerging aspects of the presentation may precede certain voluntary movements of attention, but they cannot precede all movements of attention and be in consciousness at all. The changing aspects,

the movements of attention, and the fixed phases of the presentation are simultaneous and correlative factors of every state of finite consciousness, in which consciousness there are no absolutely fixed, unchanging elements separated in time. In the process of perception, consciousness constructs fixed objects of sense upon the differentiations of the continuum, regarding each object as a synthesis of fixed component elements, each of which in turn is again regarded as composed of still lower analytic data, and so on ad infinitum. Every possible sense-object thus becomes, under the movements of attention, according as the movement is synthetic or analytic, either an analytic component element of a higher continuum, or a synthetic continuum of lower analytic data. There is no ultimate stoppingplace in consciousness where the analytic datà can be, or correspond to, simple sensations or ultimate units of consciousness. The three characteristics of consciousness, changing aspects, movements of attention, and fixed phases of the presentation, correspond to the (1) individual element related through (2) functions of the will to (3) the universal element. Thus, corresponding to the individual and the universal elements, are the two aspects of the sentient phase of consciousness termed, respectively, feeling and thought; and these two phases are related to each other through the motive phase, the will. Each of these factors of consciousness, feeling, thought, and will, according as it is referred to the ego or the non-ego, assumes a subjective or an objective form. The subjective form of the will, the adjustment of the ego to the non-ego, is attention; the objective form, the adjustment of

the non-ego to the ego, is volition. The subject

ive form of thought is self-consciousness, the objective form is intellection. The subjective form of feeling is, as yet, without a name, except as it is referred to as pleasure and pain. A very appropriate and convenient name for it would be pathy, by which name it will be designated hereafter in these pages. The objective form of feeling is sensation. Prof. Bain expresses

this fact very neatly as follows: "A sensation is, properly speaking, a sensum, a phase of our objective consciousness." This, of course, as has been repeatedly stated, does not mean that so-called subjective percepts, such as colors, sounds and tastes, are sensations; for all such percepts involve the a priori principles of intellection as well as sensation. In so far as such percepts can be described in terms of universal application, giving causal, spatial and temporal relations, they involve the a priori principles of intellection; and in so far as their character is variable for each individual perceiving subject, in so far as they can be described only by comparing them with one another, when such comparison is not known to be identical for all perceiving subjects, they involve sensation. Sensation and intellection cannot be regarded as component elements of sense-objects. In so for as sense-objects can be analyzed, they are composed of lesser sense-objects; and their different qualities, such as form, color, taste, etc., are but their appearances to different sense-organs, singly or in groups, each of which appearances involves both sensation and intellection. Consciousness is a unity; and the sense-world is a continuum, complex in its differentiations. Yet each object gets meaning only as it is related to the whole continuum. Consciousness cannot begin in disconnected states of any kind. To be conscious is to be a unity, conscious of a continuum; and the presentation continuum, in its earliest stages, is a complex unity presenting both aspects, sensation and intellection.

In giving final definitions to psychological terms, it is necessary to notice the double use made of many of them. The same term is used to denote either an activity of consciousness, or the product resulting from such activity. In some cases kindred terms are used, such as conception and concept, perception and percept. The nature of sense, sensation, intellect and intellection, and also their relation to each other and to consciousness as a whole, can best be shown by the following tabulation:

1 "The Senses and Intellect," 3d Ed., p. 382.

In the above tabulation, every term represents consciousness as a unity, viewed in some correlative phase, aspect, form, or state; e. g., "Sensation" represents consciousness in the objective form of the individual aspect of the sentient phase.

In addition to the generic meaning of the term sensation, as indicated in this tabulation, it has two specific meanings, which are of frequent use. In psycho-physical measurements, it is used to designate a simple percept of any single sense; and in psychological analysis it is used to designate any least possible change in the sensational aspect of the presentation continuum. It would be well if the term percept could supplant the use of the term sensation in all psycho-physical measurements, for then the term sensation would have but one generic and one specific meaning, and all ambiguity would thus be avoided.

PART III.

PHYSICAL CONDITIONS OF SENSATION.

CHAPTER I.

PRELIMINARY OUTLINE.

§ 1. Limits to Physical Analysis.-In passing from the mental to the physical conditions of sensation, one might at first expect to pass from the changeable to the fixed. Such expectation, however, if entertained, soon vanishes. In a certain sense the physical is more fixed than the mental; but in the physical conditions of sensation there is such an endless complexity of detail, forever dissolving before a critical analysis into still lower minutiæ, that no fixed limit can be named from which to start definition and classification. The only ultimate startingplace would be the atom of matter and the undulation of force; but these are entirely beyond empirical analysis, and so are even less satisfactory than the ever changing presentations of consciousness.

§ 2. Doubtful Problems.-Doubt exists concerning the number of senses and the character of the functions of some of them. The so-called sense of touch includes several senses, the number and character of which are still undetermined. The existence of three, the tactual, the muscular, and the thermal, appears to be established beyond reasonable doubt. Two others, the sense of the articular cartilages and the sense of innervation, are still in dispute.

Doubtful points concerning the exact nature of nervestimuli can probably never be determined. The nature of